Recently, with the rapid development and application of information technology, wireless mobile telecommunication, and information domestic appliances, information products like a mobile phone, a notebook computer, a multimedia player, and an automatic service terminal have changed from the conventional inputting manner by a keyboard or mouse to touching, for the purpose of convenience, compactness, and humanization. A touch display panel generally is divided into a capacitor type, a resistor type, and a photo sensitive type. In all touch display panels, the accuracy for sensing a finger is a key point in design. A pressure sensing technique refers to a technique in which an external force is detected. This technique is used to measure a pressure from the environment or a pressure from a finger of a user, and the result of this pressure measurement is used for adjusting touch function, or for human-computer interactive experience.
The pressure sensing technique is divided into the following types. For example, in a capacitor type pressure detection manner, an electrode layer in the display panel is generally used as a reference, and another electrode layer is formed separately as a sensor. Pressing induces mechanical deformation, and this leads to variation in capacitance between two electrode layers, which is applied to detect pressure. However, the capacitor type pressure detection poses strict requirements for parasitic capacitance parameters of the electrodes, is difficult to realize, and is liable to fail on a dirty surface or in a humid environment. For example, in a piezo-resistant strain manner, pressing induces variation in impedance of a piezo-resistant electrode, which is applied for pressure sensing. Since pressing induces minor variation in impedance of the piezo-resistant electrode, it is difficult to sense and is liable to fail. Meanwhile, the conventional capacitor type pressure detection and piezo-resistant strain detection generally introduce additional a sensing structure (e.g., sensor in the capacitor type pressure detection, or the piezo-resistant electrode in the piezo-resistant strain detection) in a back light module of the liquid crystal display (LCD) or a middle frame of the mobile phone. This kind of design requires to modify the structural design of the display panel. The fitting tolerance is relatively large, which leads to a low pressure sensing accuracy.